Physics – Condensed Matter – Other Condensed Matter
Scientific paper
2010-05-28
Physics
Condensed Matter
Other Condensed Matter
Scientific paper
We measure the power spectral density of frequency fluctuations in nanocontact spin torque oscillators over time scales up to 50 ms. We use a mixer to convert oscillator signals ranging from 10 GHz to 40 GHz into a band near 70 MHz before digitizing the time domain waveform. We analyze the waveform using both zero crossing time stamps and a sliding Fourier transform, discuss the different limitations and advantages of these two methods, and combine them to obtain a frequency noise spectrum spanning more than five decades of Fourier frequency $f$. For devices having a free layer consisting of either a single Ni$_{\text{}80}$Fe$_{\text{}20}$ layer or a Co/Ni multilayer we find a frequency noise spectrum that is white at large $f$ and varies as \emph{$1/f$} at small $f$. The crossover frequency ranges from $\approx\unit[10^{4}]{Hz}$ to $\approx\unit[10^{6}]{Hz}$ and the $1/f$ component is stronger in the multilayer devices. Through actual and simulated spectrum analyzer measurements, we show that $1/f$ frequency noise causes both broadening and a change in shape of the oscillator's spectral line as measurement time increases. Our results indicate that the long term stability of spin torque oscillators cannot be accurately predicted from models based on thermal (white) noise sources.
Keller Mark W.
Pufall Matthew R.
Rippard William H.
Silva Thomas J.
No associations
LandOfFree
Non-white frequency noise in spin torque oscillators and its effect on spectral linewidth does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Non-white frequency noise in spin torque oscillators and its effect on spectral linewidth, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-white frequency noise in spin torque oscillators and its effect on spectral linewidth will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-16643